Network Node, User Equipment and Methods Performed Therein

Abstract

Embodiments herein relate, for example, to a method performed by a network node ( 150,13,15 ) for handling registering to an Internet Protocol Multimedia Subsystem, IMS, network in a communication network. The network node, with the proviso that a user equipment, UE, ( 10 ) is performing a handover from a first public land mobile network, PLMN, of a first country or operator to a second PLMN of a second country or operator, performs one or more of the following: —enforcing the UE ( 10 ) to make a session initiation protocol, SIP, registration whereby an IMS system can switch off SIP encryption policy, immediately after having entered the second PLMN; —initiating a SIP re-INVITE with a session description protocol, SDP, including a UE subscriber identity, ID, a remote party ID, and an indication of a speech codec; and 7 or —when the network node knows by configuration that the second PLMN requires a different SIP encryption policy than currently used, sending a message to another network node, wherein the message indicates explicitly or implicitly that a different SIP encryption policy and/or LI policy is to be used.

1 - 12 . (canceled) 
     
     
         13 . A method, performed by a network node, the method comprising:
 handling registration of a User Equipment (UE) to an Internet Protocol Multimedia Subsystem (IMS) network in a communication network;   wherein the UE is performing a handover from a first public land mobile network (PLMN) of a first country or operator to a second PLMN of a second country or operator.   
     
     
         14 . The method of  claim 13 , wherein the handling of the registration comprises enforcing the UE to make a session initiation protocol (SIP) registration, the IMS system being capable of switching off a SIP encryption policy immediately after the UE has entered the second PLMN. 
     
     
         15 . The method of  claim 13 , wherein the handling of the registration comprises initiating a SIP re-INVITE with a session description protocol (SDP) including a UE subscriber identity (ID), a remote party ID, and an indication of a speech codec. 
     
     
         16 . The method of  claim 13 , wherein:
 the handling of the registration comprises sending a message to another network node;   the message indicates explicitly or implicitly that a different SIP encryption policy and/or Lawful Intercept (LI) policy is to be used; and   the network node knows by configuration that the second PLMN requires a different SIP encryption policy than currently used.   
     
     
         17 . The method of  claim 13 , further comprising responding to a SIP invite from the UE or a Serving Call Session Control Function (S-CSCF) with an error message in response to detecting that the UE has changed to the second PLMN. 
     
     
         18 . The method of  claim 13 , wherein the network node is of the second PLMN and subject to idle mode mobility and the method further comprises:
 receiving a tracking area update (TAU) request from the UE; and   rejecting the TAU request with an indication that the UE shall reconnect followed by the establishment of a protocol data network (PDN) connection to an IMS access point name (APN) and an initial SIP registration over the PDN connection.   
     
     
         19 . The method of  claim 13 , wherein the network node is of the second PLMN and the method comprises detecting a voice bearer release and disconnecting a PDN connection of the UE with an instruction to the UE to reconnect. 
     
     
         20 . The method of  claim 13 , further comprising detecting a PLMN change for the UE. 
     
     
         21 . A method, performed by a user equipment (UE), of handling communication of the UE in a communication network, the method comprising:
 obtaining an indication that the UE is performing a handover from a first public land mobile network (PLMN) of a first country or operator to a second PLMN of a second country or operator;   changing PLMN and initiating a session initiation protocol (SIP) re-register.   
     
     
         22 . The method of  claim 21 , wherein obtaining the indication comprises determining that the UE is performing the handover or receiving the indication from a network node. 
     
     
         23 . A network node comprising:
 processing circuitry and memory, the memory storing instructions executable by the processing circuitry whereby the network node is configured to:
 handle registration of a User Equipment (UE) to an Internet Protocol Multimedia Subsystem (IMS) network in a communication network, 
   wherein the UE is performing a handover from a first public land mobile network (PLMN) of a first country or operator to a second PLMN of a second country or operator.   
     
     
         24 . The network node of  claim 23 , wherein to handle the registration the network node is configured to enforce the UE to make a session initiation protocol (SIP) registration, the IMS system being capable of switching off a SIP encryption policy immediately after the UE has entered the second PLMN. 
     
     
         25 . The network node of  claim 23 , wherein to handle the registration the network node is configured to initiate a SIP re-INVITE with a session description protocol (SDP) including a UE subscriber identity (ID), a remote party ID, and an indication of a speech codec. 
     
     
         26 . The network node of  claim 23 , wherein:
 to handle the registration the network node is configured to send a message to another network node;   the message indicates explicitly or implicitly that a different SIP encryption policy and/or Lawful Intercept (LI) policy is to be used; and   the network node knows by configuration that the second PLMN requires a different SIP encryption policy than currently used.   
     
     
         27 . The network node of  claim 23 , wherein the network node is further configured to respond to a SIP invite from the UE or a Serving Call Session Control Function (S-CSCF) with an error message in response to detecting that the UE has changed to the second PLMN. 
     
     
         28 . The network node of  claim 23 , wherein:
 the network node is of the second PLMN and subject to idle mode mobility;   the network node is further configured to:
 receive a tracking area update (TAU) request from the UE; and 
 reject the TAU request with an indication that the UE shall reconnect followed by the establishment of a protocol data network (PDN) connection to an IMS access point name (APN) and an initial SIP registration over the PDN connection. 
   
     
     
         29 . The network node of  claim 23 , wherein the network node:
 is of the second PLMN; and   is further configured to detect a voice bearer release and disconnect a PDN connection of the UE with an instruction to the UE to reconnect.   
     
     
         30 . The network node of  claim 23 , wherein the network node is further configured to detect a PLMN change for the UE. 
     
     
         31 . A user equipment (UE) comprising:
 processing circuitry and memory, the memory storing instructions executable by the processing circuitry whereby the UE is configured to:
 obtain an indication that the UE is performing a handover from a first public land mobile network (PLMN) of a first country or operator to a second PLMN of a second country or operator; 
 change PLMN and initiate a session initiation protocol (SIP) re-register. 
   
     
     
         32 . The UE of  claim 31 , wherein to obtain the indication the UE is configured to determine that the UE is performing the handover or receive the indication from a network node.